Exhaust systems of this type are in particular used in series production in motor vehicles to influence the noise emission of the internal combustion engine. DE 197 43 446 A1, for example, describes an exhaust system for an internal combustion engine which ensures good sound absorption over the whole frequency range with respect to a reduced noise level of motor vehicle engines and nevertheless does not allow the exhaust pressure to increase too highly even at a high internal combustion engine speed. For this purpose, two parallel mufflers are provided which are tuned to different frequencies. Both mufflers are operable as flow-permeated reflection mufflers, on the one hand; on the other hand, a discharge of the exhaust flow from the muffler can be prevented by closing the outlet pipe of a muffler by means of an exhaust flap so that it then acts as a Helmholtz resonator.
The exhaust system described by DE 197 43 446 A1 comprises an exhaust train which is made in parallel sectionally. In accordance with the embodiments, the exhaust flow is supplied to the two mufflers at the inlet side via a common forking exhaust pipe and/or is merged and led away via a common exhaust pipe at the outset side or, respectively, a double-fork-like double junction is provided as a cross-position.
With an arrangement of this type, the typical sound of an internal combustion engine comprising at least two cylinder banks, such as a V8, is disadvantageously lost. In particular, the vibrations of odd orders are lost; the ignition order (4th order of vibrations) and its harmonic dominate. Attributes such as force and power can only be represented by volume so that a conflict is present in this respect with the comfort demand made on the drive.
The crankshaft of multi-cylinder internal combustion engines is produced by arranging the crank throws of the individual cylinders in rows next to one another. When fixing the throw sequence, it is important to observe an ignition sequence which is as smooth as possible, a mass balancing and the rotary oscillations. The changing cylinder pressures which act on the exhaust system in dependence on the throw sequence and on the ignition sequence via the outer structure-borne route make a decisive contribution to the characteristic sound of the internal combustion engine.
With V8 internal combustion engines, for example, a customary ignition sequence is 1-5-4-8-6-3-7-2, with the cylinders 1-4 being associated with one cylinder bank and the cylinders 5-8 being associated with the other cylinder bank. On the basis of this ignition sequence, significant frequency proportions arise in the oscillations of odd orders since, for example, 270° crankshaft lie between cylinders four and three on the one cylinder bank and only 90° crankshaft between cylinders two and one. The excitation spectra on the exhaust side of both cylinder banks are in turn identical, but phase shifted, to one another.